Printing telegraph mechanism

ABSTRACT

The styli of a mosaic printhead are each attached to switchable conductive loops positioned in a gap between a pole piece and a rotatable magnetic member. The rotatable member is rotated continuously and periodically induces currents in closed, conductive short circuited loops thus causing them and their associated styli to move.

United States Patent [1 1 Taylor Aug. 20, 1974 PRINTING TEIZEGRAPI-IMECHANISM [75] Inventor: Terrence Francis Edward Taylor, [56] ReferencesCited Burgess Hill, England UNITED STATES PATENTS 73 AssigneezInternational standard Electric 3,477,365 11/1969 Nyman 346/141 XCorporation, New York, N.Y. Primary Examiner-Thomas A. Robinson [22]Flled: June 1, 1973 Attorney, Agent, or Firm-A. Donald Stolzy [21] Appl.No.: 366,220

' [57] ABSTRACT [30] Foreign Application Priority Data The styli of amosaic printhead are each attached to J 97 switchable conductive loopspositioned in a gap beune l, 1 2 Great Britain 25597/72 tween a p pieceand a rotatable magnetic member The rotatable member is rotatedcontinuously and pe- [52] Cl 178/30 178/33 3 5 35 riodically inducescurrents in closed, conductive short [51] Int Cl 9/38 H041 21/00circuited loops thus causing them and their associated [58] Field ofSearch 178/17 R, 27, 30, 33; move 346/141; 310/103, 105; 335/229; 197/1R 10 Claims, 15 Drawing Figures 7/ @4 Z9 78 /0 p 5 ['1 5 ll 75 Pmmzuwczm 3.830.976

' slmws FIGM.

v 1 PRINTING TELEGRAPH MECHANISM BACKGROUND OF THE INVENTION Thisinvention relates to the art of serial printing, and more particularly,to a method of printing mosaic characters.

In the past, it has been the practice to print a mosaic character byemploying a vertical column of styli equal to the character height andprinting no dots or one or more dots by styli actuation at successivedifferent horizontally spaced columns over a character width. Typicallya column from 7 to 15 styli may be employed at from to 9 of saidhorizontal locations. The styli spacing is conventionally, but notnecessarily, uniform. So is the location spacing. These two may or maynot be equal, as desired.

The styli are typically mounted on a movable carriage on which styliactuators are supported. The actuators and other apparatus on thecarriage increase the inertia thereof and decrease its advancing andreturn acceleration, deceleration and velocity, both maximum andaverage. This is a disadvantage in the operation of a high speedmachine.

SUMMARY OF THE INVENTION In accordance with the mechanism of the presentinvention, the above-described and other disadvantages of the prior artare overcome by utilizing a lightweight induced current activatedconductive loop to operate a stylus.

The above-described and other advantages of the present invention willbe better understood from the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of aconventional mosaic printer;

FIG. 2 is a sectional view of a portion of a stylus head, a portion ofwhich may be employed with the present invention;

FIG. 3 is a top plan view of a portion of a recording medium in fivestates of the development of a mosaic character thereon, the characterbeing the numeral 7;

FIG. 4 is a view similar to FIG. 2, but modified in accordance with thepresent invention;

FIG. 5 is a perspective view of an electromagnetic arrangementconstructed in accordance with the present invention;

FIG. 6 is a perspective view of a rotatable magnetic member, conductiveloops and a switch;

FIGS. 7 and 8 are end elevational views of two alternative embodimentsof the present invention;

FIG. 9 is a perspective view of apparatus similar to that illustrated inFIG. 1 modified as in FIG. 4;

FIG. 10 is a side elevational view of a portion of the apparatus of thepresent invention;

FIG. 11 is a transverse sectional view of a stylus portion and supporttube portion taken on the line 11-11 shown in FIG. 10;

FIG. 12 is a top plan view of the apparatus shown in FIG. 10;

FIGS. 13 and 14 are alternative embodiments of the present invention;and

FIG. 15 is a block'diagram of a telegraphic machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional prior art mosaicprinter is shown in FIG. 1 including an input circuit 20 which receivesand stores, for example, a serial binary code which determines which, ifany, of a plurality of styli in a column are to be employed to printdots on a recording medium. Input circuit 20 thus controls a stylus head21 and the individual styli thereof through a stylus control 23. Inputcircuit 20 also controls a roll control 24 for a roll 25 which supportsa recording medium 26 such as inked paper. Input circuit 20 alsocontrols a carriage control 27 which pulls a carriage 28 in a directionto the right, as viewed in FIG. 1, against the force of a spring 29which is fixed at its left end connected to carriage 28 at its rightend. Head 21 is fixed to carriage 28. Carriage 28 has a single guide 30in which carriage 28 is guided by a tongue 31 that fits in a groove 32of channel 30.

As shown in FIG. 2, stylus head 21 includes a rearwall 33 and a frontwall 34.

In FIG. 2, a stylus 36 is slidable through a hole 37 in wall 34. Asolenoid winding 38 is fixed to wall 34. Stylus 36 is thus slidablethrough winding 38. A coiled spring 39 rests against the right end ofwinding 38 and urges stylus 36 in a direction toward wall 38. Stylus 36has a flange 40 fixed to the end thereof which is pressed against wall33 by spring 39. Movement of stylus 36 in a direction to the left, asviewed in FIG. 2, is stopped by engagement of flange 40 with a flange 41on a cylinder 42 fixed to wall 33.

In the prior art, and in accordance with the present invention, dots maybe made on paper 26 by the impact of the end of a stylus thereagainst.

In the prior art, a mosaic character may be formed as shown inFIG. 3 Thesame portion of a recording medium is illustrated at 43, 44, 45, 46 and47. It will be understood when no solenoid corresponding to solenoid 38in FIG. 2 is energized for any of the styli 22 shown in FIG. 1, a spacewill be left on the recording medium. However, this space will not beone character space, but, for example, may be only one-fifth of acharacter space. When one or more dots in one column are produced, allof these dots may be made simulta* neously.

As shown in FIG. 3, the dot in rectangle 43 is made before the otherdots are made. Dots 48, 49, 50 and 51 then may be made simultaneouslythereafter. One or more additional dots are added in each column untilthe numeral seven is portrayed in rectangle 47.

In accordance with the present invention, the chronological order inwhich the dots are made may or may not be as described hereinbefore andas shown in FIG. 3.

A stylus head 21' is indicated in FIG. 4. A stylus 36' is shown in FIG.4 slidable through a hole 37' in a wall 34. A hollow cylinder 38 may beslidable on stylus 36' or fixed to wall 34, if desired. In either event,stylus 36' is slidable through cylinder 38'. A coiled spring 39' restsagainst the right end of cylinder 38' and urges stylus 36' in adirection toward a wall 33'. Stylus 36' has a flange 40' fixed relativethereto which is pressed against wall 33' by spring 39'. Movement ofstylus 36' in a direction to the left, as viewed in FIG. 4, is stoppedby engagement of flange 40 with a flange 41 on a cylinder 42' fixed towall 33'.

Note will be taken that the stylus head 21' in FIG. 4 does not differ agreat deal from the stylus head 21 in FIG. 2. One difference is that, inFIG. 4, cylinder 38 replaces solenoid winding 38 in FIG. 2. Stillfurther, rear wall 33 has a hole 37" therethrough through which anextension 36" slides.

In some cases, all of the structures illustrated between the walls 33'and 34' may be omitted with the exception of stylus 36. In some cases,flange 40 may also be omitted. Note will be taken that, as shown, stylus36', flange 40' and extension 36" are fixed relative to each other.

Because of the mass of a print wheel which bears all the symbols likelyto be required at a given time by a dataprinter, and of the time takento position a required symbol at the point of printing, the developmentof mosaic printers has been looked upon favorably. In these printers,symbols to be printed are built up by the selective printing of dots atpositions in an array, usually rectangular, of possible positions. Arectangular array of 35 dots, seven rows by five columns enables areadable representation off the roman letters and arabic numerals to beobtained. Instead of using 35 printing styli, or needles, and selectingall those needed for a particular symbol at the same time, mass can besaved by printing the five columns in succession, using only sevenneedles. In one commercially available printer of this kind, each needleis driven by its own individual solenoid, the mass of which is some 30grams. In the interest of speed and reduced wear, it is desirable toreduce this mass even further. This is accomplished in accordance withthe present invention.

In the drawings, in FIG. 5, a magnetic yoke 101 is shown. It is ofsubstantially U-shaped cross section which is at least as long as arecord web is wide. The record web is that on which the symbols areprinted. One limb 102 of the yoke 101 is shaped as a pole piece andanother limb 103 cooperates with a short pole piece 104 attached to aprinthead carriage. The pole piece 104 causes a local concentration ofthe magnetic flux produced by the magnetic at the place where it is mostuseful and so helps to reduce power supply requirements.

A conductive coil 55 encircles a third limb 56 which joins togetherlimbs 102'and 103. By means of electric current in this coil, themagnetic assembly can be energized. Alternatively, yoke 101 and itslimbs 102 and 103 and winding 55 are shorter than the web width, but arereplicated across it and are energized in succession, this againreducing the power supply requirements.

A rotatable magnetic member 57 coextensive at least with the width ofthe record web is mounted to rotate around an axis parallelto its lengthbetween the pole pieces, fitting closely in the curved pole piece oflimb 102, but being separated from the pole piece 104 by a distancesufficient to allow a conductive loop 58 to perform a linear movementgenerally perpendicular to the length of the pole piece and to therecord web. The loop, which is rigid, is rigidly connected to a printingneedle carried on the printhead carriage, which can be made to traversethe width of the record web in order to print a line of graphicalsymbols. As many loops 58 as there are printing needles are provided. Toeach loop 58 there may or may not be connected a switch 59 as shown inFIG. 6 through trailing conductors or slip rings, for instances. Thepole piece 104 is long enough to cover the loops of all the needleswhich may be actuated at any one instant.

The rotatable member 57 is caused to rotate continuously by asynchronous motor M or a motor synchronous with the incoming message.Motor M may be shut down, on occasion, if desired.

If motor M is synchronous with the incoming data, the column print datashould be spaced in some cases to prevent a printout in two columns.

If motor M is a synchronous motor, it should be fast enough to produceone stylus movement for each set of column data. The data for one columnshould also be spaced in time to prevent a printout in two columns orbetween columns.

Motor M is energized at least while the yoke 101 is energized. When anyswitch 59 is closed, cyclic flux variations, when motor M is running andwinding 55 is energized, induce a current in the appropriate conductiveloop 58 which sets up its own magnetic field. The interaction of themagnetic field produced by the induced current and the field in the gapbetween pole pieces 104 and rotatable member 57 causes the loop, and theneedle rigidly connected thereto, to move towards the record web, theneedle thereby printing a dot. This happens as the narrow face of therotatable member 57 moves to a position at or near conductive loop 58.Thus, by selective closure of the switches 59, selected loops 58 andtheir associated needles are moved.

The switches 59 are controlled either from a key board or by signalsreceived from some more or less remote source, and may be any kind ofswitching device which when closed, or in a conducting condition, offersnegligible impedance to the induced currents in an associated loop.

In FIG. 7, a different yoke arrangement is shown. l-lere limbs 102' and103' and pole piece 104' are as in FIG. 5, but the coil 55 is dispensedwith and a permanent magnet forms the limb 56.

Yet another arrangement is shown in FIG. 8. Here limbs 102", 103" and56" are as in FIGS. 5 and 6, as is pole piece 104", but rotating member57" is itself a permanent magnet. This arrangement, of course, causescomplete flux reversal within the magnetic yoke for each rotation of themember 57".

Pole piece 104 may be coextensive with limb 103 and attached theretoinstead of being carried on the printhead, although this does notconserve power as does the travelling pole piece.

In FIG. 9, a carriage 60 rolls on a track 61 having rails 62 and 63.Carriage 60 and wheels 64 that roll on track 61. A support and guideplate 65 is fixed to carriage 61. Styli 66 are movable through plate 65.A record web 67 is indicated adjacent styli 66.

In FIG. 10, a magnetic yoke 101' is illustrated with an energizingwinding 55'. Yoke 101' has a stationary upper limb 103" and a stationarylower limb 102". A rotatable magnetic member 57" is fixed to androtatable by and with a drive shaft 68. A traversing pole piece 104" isshown adjacent the limb 103". A pole piece support beam 69 rigidlyconnects pole piece 104" with a support and guide plate 70. A rearsupport and brace 71 is fixed to beam 69 and a carriage 72. Brace 71also has a support tube 73 fixed thereto through which a stylus 74 isslidable. Carriage 72 has wheels 75 as before, which travel on rails 76.A conductive loop 77 is fixed to stylus 74. A platen 78 is provided onwhich a'web 79 is movable. Platen 78 rolls, but need not have acarriage. It can stay in a fixed axial position.

Plate 70 may or may not be identical to stylus head 21 of FIG. 4.

In FIG. 10, stylus 74 may have a uniform circular cross sectionthroughout its length except for a square portion thereof shown in tube73. Tube 73 may or may not be square in cross section throughout itsentire length. However, it is square over a portion of its length thatstylus 74 is square. Alternatively, no means or some other means may ormay not be provided to keep stylus 74 and loop 77 from turning about theaxis of stylus 74. Stylus 74 may or may not be spring biased.

In FIG. 12, stationary upper limb 103" is again shown with drive shaft68, rotatable magnetic member 57", stationary lower limb 102",traversing pole piece 104", conductive loop 77, pole piece support beams69, support tube 73, brace 71, carriage 72, rails 76, plate 70, stylus74, and web 79. Note will be taken that there are two pole piece beams69 in both of the FIGS. and 12.

In FIG. 15, a telegraphic machine is indicated at 80 having telegraphiclines 81 and 82 connected thereto. Telegraphic machine 80 has input andoutput units 83 and 84, respectively. Telegraphic machine 80 also has atape punch 85, a keyboard to telegraph code converter 86, a tape reader87, a telegraph code to mosaic pattern coverter 88, a stunt box 89, akeyboard unit 90, and a printing unit 91.

Telegraphic lines 81 and 82 are connected to input unit 83. Converter 86and tape reader 87 are connected to the input of output unit 84. Theoutput of output unit 84 is connected to telegraphic lines 81 and 82 Theoutput of tape reader 87 is also connected to converter 88 and tapepunch 85. The output'of con verter 86 is connected to one input of stuntbox 89, one input to converter 88 and to one input of tape punch 85.

The output of input unit 83 is connected to still another input of tapepunch 85, to still another input of converter 88 and to still anotherinput of stunt box 89.

Converter 86 receives an input from keyboard unit 90. Printing unit 91receives inputs from outputs of converter 88 and stunt box 89.

In review, mosaic printheads have been developed by Philips, as well asseveral others, including that used in the teleprinter manufactured byExtel Corporation of Chicago, Illinois. These printheads build upcharacters as a pattern of dots in a possible matrix of 7 X 5 dots.Instead of employing 35 styli and energizing all the styli needed for acharacter at the same time, they have only 7 stylie arranged in avertical column and form a character by selectively energizing the styliat five postions, one after the other, much in the way described incopending application Ser. No. 295,154, filed Oct. 5, 1972, by T. J.Holland for PRINTING METHOD, now US. Pat. No. 3,757,346.

These printheads carry individual motors for each stylus on theprinthead, in the case of the Philips head, seven motors being needed.(By motor," we mean an actuating device for moving the stylus, notnecessarily a rotating electrical device. Thus, a solenoid is a motor,and so is a piezoelectric bimorph.) In order to deliver a sufficientlygreat impact to print these motors must be reasonably powerful. Thismeans that the printhead is carrying a fair amount of mass.

A lightweight printhead is desirable so that it can be traversed acrossthe record web at high speeds, particularly, in carriage return. Itwould, therefore, be of advantage if the head carried only the styli andthe supports therefor and as little else as possible, ideally as shownherein.

In FIG. 9, carriage 60 runs on rails and has the support and guide platethrough which 7 styli 66 protrude towards a record web 67.

Some form of motor must move the styli 66 towards the web 67 in orderthat printing may take place. In accordance with the present invention,the back ends of the styli 66 (the ends remote from the web 67) haverigid conductive loops 77 attached thereto by motion transmitting means.The motion transmitting means (e.g., connection means between drivermeans and the styli 66) may be directed rigid rods, or Bowden cableslike bicycle hand brake cables. In accordance with the presentinvention, loops 77 moving with the printhead are influenced by, not asingle motor per stylus, but a common motor, which common motor doesnot, of itself, traverse the web 67, but is instead coextensive with thewidth of the web 67. All the loops 77 for each stylus 66 are infleunced,when the loop is complete, by the one motor. The motor is, if you like,an electromagnetic printing bail.

Only one 74 of several styli have been shown in FIG. 10 for clarity. Theother styli, if connected to their loops by rigid rods would have topass through the supports at angles to each other so as to hit the webin a vertical line. See FIG. 13. If connected by Bowden cable, theycould be in line at the support plate. See FIG. 14.

Some of the dimensions have been greatly exaggerated for clarity. Theloops would be much smaller in width so that all could sit side by sideunder the traversing pole piece.

An alternative to the travelling pole piece would be to have astationary pole piece coextensive with the stationary upper limb, thustaking some weight off the traversing printhead. Such a stationary polepiece would, of course, be integral with the stationary upper limb, thuseliminating the air gap.

The rotating magnetic member is rotated at a constant speed by somesuitable drive means as long as the printer is in use. The grooves shownin FIGS. 5 and 8 cause the flux to swing back and forth across the loopsat a greater rate than it would if it depended on the speed of rotationof the rotating magnetic member alone.

The printhead forms part of a printing unit which in turn is part of atelegraphic machine, for example,-a teletypewriter or teleprinter. FIG.15 shows the basic units of such a machine. The input unit acceptstelegraph signals from the line and renders them suitable for use withinthe machine. The telegraph code to mosaic pattern converter does exactlywhat its name implies producing at its output signals with which tooperate the printing unit; such a unit has been described before.

In the event that some question arises concerning the structure oroperation of converter 88, two patents disclosing both are, by thisreference hereto, hereby incorporated herein as though fully set forthhereat. These patents are British Pat. No. 1,240,477 and Swiss Pat. No.501,971.

The stunt box is a well-known unit which transforms the appropriatetelegraph signals into commands to line feed, carriage return, space, etcetra. The keyboard unit generates signals, possibly in its own code, tobe applied to the output unit or the printing unit or the tape punch orany combination of the three. The tape reader generates signals to beapplied to the same three units in any combination. The keyboard code totelegraph code converter does exacctly what its name implies, assumingthat the keyboard does not produce telegraph code directly (otherwisethe converter is unnecessary). The output unit renders the signals inthe machine suitable for application to the telegraph line.Interconnections between the units have been shown as single lines;however, the intramachine signals may be handled in parallel overmultiple con nections.

Although the apparatus of the present invention may be used in punchedtape or other applications, it most likely will be used more byrepeatedly striking paper (web) on a platen with one or more stylisimultaneously or consecutively to provide a dot mosaic inked letter,number, character or otherwise. Any means may be employed to provide ornot to provide the ink, as desired. An inked ribbon may be used. It isalso well known that a character may be produced by striking aconventional inked paper which carries its own ink. Paper 79 shown inFIG. 10 may be such inked paper, if desired. Many other suitable inkingmethods and equipments will also be obvious to those skilled in the art.

As stated previously, stylus head 21' shown in FIG. 4 or anymodification thereof may be substituted for plate 70 in FIG. 10.

The word carriage is hereby defined for use hereinbefore and hereinafterand for use in the claims to mean something that carries something else,and may either be movable or be fixed unless its mobility or the lack ofit is specifically and expressly stated.

The phrase carriage means is hereby defined for use hereinbefore andhereinafter and for use in the claims to mean one or more structuresand/or a carriage as that word carriage is defined in the immediatelypreceding paragraph.

The phrase connecting means is hereby defined for use herein and for usein the claims to mean either an electrical conductor integral or notwith the conductive loop or a switch or otherwise.

What is claim is:

l. A printer comprising:

a base;

a carriage means mounted on said base;

platen means mounted on said base in a manner to support a recordingmedium adjacent said carriage means;

an elongated axially movable stylus having first and second ends;

a conductive loop fixed relative to said second stylus end;

means to produce relative movement between a recording medium and saidfirst stylus end in a direction approximately normal thereto;

means mounted on said carriage means to guide said axial movement ofsaid stylus;

driver means to produce magnetic flux in a location linking saidconductive loop, said driver means causing the amount of said linkingflux to change abruptly; and

a selectively operable switch connected in series with said conductiveloop to short circuit the same when the switch is closed, said abruptchange in flux leaving said conductive loop axially motionless when saidswitch is open, said abrupt change in flux causing a force to be appliedto said conductive loop when said switch is closed, said force beingtransmitted to said stylus to move the same axially to cause said firstend thereof to strike a recording medium when such is supported inposition therefor by said platen means as aforesaid, and to make adetectable recording mark on said recording medium where said stylusfirst end strikes said record medium, closure of said switch permittinga current to be induced in said conductive loop, which induced currentproduces its own magnetic field that reacts with that produced by saiddriver means and causes said force to be applied to said conductiveloop.

2. The invention as defined in claim 1, wherein:

means are provided to prevent said conductive loop from rotating aboutthe axis of said stylus.

3. The invention as defined in claim 2, wherein:

a spring is provided, said spring being mounted on said carriage meansto urge said stylus in a direction away from said platen means.

4. The invention as defined in claim 3, wherein:

said driver means includes a magnetic circuit having a fixed magneticyoke including an elongated, noncircular magnetic shaft spaced a shortdistance therefrom, a maximum flux being established in said magneticcircuit when said shaft is located in one angular position, a minimumflux being established in said magnetic circuit when said shaft islocated in another angular position, means to rotate said shaft, meansto establish a magnetomotive force in said magnetic circuit, saidconductive loop being located between one end of said yoke and saidshaft.

5. The invention as defined in claim 2, wherein:

said driver means includes a magnetic circuit having a fixed magneticyoke including an elongated, noncircular magnetic shaft spaced a shortdistance therefrom, a maximum flux being established in said magneticcircuit when said shaft is located in one angular position, a minimumflux being established in said magnetic circuit when said shaft islocated in another angular position, means to rotate said shaft, meansto establish a magnetomotive force in said magnetic circuit, saidconductive loop being located between one end of said yoke and saidshaft.

6. The invention as defined in claim 1, wherein:

spring is provided, said spring being mounted on said carriage means tourge said stylus in a direction away from said platen means.

7. The invention as defined in claim 6, wherein:

said driver means includes a magnetic circuit having a fixed magneticyoke including an elongated, noncircular magnetic shaft spaced a shortdistance therefrom, a maximum flux being established in said magneticcircuit when said shaft is located in one angular position, a minimumflux being established in said magnetic circuit when said shaft islocated in another angular position, means to rotate said shaft, meansto establish a magnetomotive force in said magnetic circuit, saidconductive loop being located between one end of said yoke and saidshaft.

8. The invention as defined in claim 1, wherein:

said driver means includes a magnetic circuit having a fixed magneticyoke including an elongated, noncircular magnetic shaft spaced a shortdistance therefrom, a maximum flux being established in said magneticcircuit when said shaft is located in one angular position, a minimumflux being established in said magnetic circuit when said shaft islocated in another angular position, means to rotate said shaft, meansto establish a magnetomotive force in said magnetic circuit, saidconductive loop being located between one end of said yoke and saidshaft.

9. An electromagnetic actuator comprising:

a base; t

a movable conductive loop for connection to a member to be mechanicallyactuated by movement thereof;

means to guide movement of said conductive loop on said base in theplane of said conductive loop;

connecting means selectively operable to open and to short circuit saidconductive loop; and

driver means to produce magnetic flux in a location linking saidconductive loop, said driver means causing the amount of said linkingflux to change abruptly for inducing a current in said conductive loop.

10. The invention as defined in claim 9, wherein:

said connecting means includes a selectively operable switch which canbe opened or closed, said switch being connected in series with saidconductive loop to short circuit the same when the switch is closed,said abrupt change in flux leaving said conductive loop motionless whensaid switch is open, said abrupt change in flux causing a force to beapplied to said conductive loop when said switch is closed, said forcebeing transmitted to said member to move the same, closure of saidswitch permitting a current to be induced in said conductive loop whichinduced current produces its own magnetic field that reacts with thatproduced by said driver means and causes said force to be applied tosaid conductive loop.

1. A printer comprising: a base; a carriage means mounted on said base;platen means mounted on said base in a manner to support a recordingmedium adjacent said carriage means; an elongated axially movable stylushaving first and second ends; a conductive loop fixed relative to saidsecond stylus end; means to produce relative movement between arecording medium and said first stylus end in a direction approximatelynormal thereto; means mounted on said carriage means to guide said axialmovement of said stylus; driver means to produce magnetic flux in alocation linking said conductive loop, said driver means causing theamount of said linking flux to change abruptly; and a selectivelyoperable switch connected in series with said conductive loop to shortcircuit the same when the switch is closed, said abrupt change in fluxleaving said conductive loop axially motionless when said switch isopen, said abrupt change in flux causing a force to be applied to saidconductive loop when said switch is closed, said force being transmittedto said stylus to move the same axially to cause said first end thereofto strike a recording medium when such is supported in position thereforby said platen means as aforesaid, and to make a detectable recordingmark on said recording medium where said stylus first end strikes saidrecord medium, closure of said switch permitting a current to be inducedin said conductive loop, which induced current produces its own magneticfield that reacts with that produced by said driver means and causessaid force to be applied to said conductive loop.
 2. The invention asdefined in claim 1, wherein: means are provided to prevent saidconductive loop from rotating about the axis of said stylus.
 3. Theinvention as defined in claim 2, wherein: a spring is provided, saidspring being mounted on said carriage means to urge said stylus in adirection away from said platen means.
 4. The invention as defined inclaim 3, wherein: said driver means includes a magnetic circuit having afixed magnetic yoke including an elongated, non-circular magnetic shaftspaced a short distance therefrom, a maximum flux being established insaid magnetic circuit when said shaft is located in one angularposition, a minimum flux being established in said magnetic circuit whensaid shaft is located in another angular position, means to rotate saidshaft, means to establish a magnetomotive force in said magneticcircuit, said conductive loop being located between one end of said yokeand said shaft.
 5. The invention as defined in claim 2, wherein: saiddriver means includes a magnetic circuit having a fixed magnetic yokeincluding an elongated, non-circular magnetic shaft spaced a shortdistance therefrom, a maximum flux being established in said magneticcircuit when said shaft is located in one angular position, a minimumflux being established in said magnetic circuit when said shaft islocated in another angular position, means to rotate said shaft, meansto establish a magnetomotive force in said magnetic circuit, saidconductive loop being located between one end of said yoke and saidshaft.
 6. The invention as defined in claim 1, wherein: spring isprovided, said spring being mounted on said carriage means to urge saidstylus in a direction away from said platen means.
 7. The invention asdefined in claim 6, wherein: said driver means includes a magneticcircuit having a fixed magnetic yoke including an elongated,non-circular magnetic shaft spaced a short distance therefrom, a maximumflux being established in said magnetic circuit when said shaft islocated in one angular position, a minimum flux being established insaid magnetic circuit when said shaft is located in another angularposition, means to rotate said shaft, means to establish a magnetomotiveforce in said magnetic circuit, said conductive loop being locatedbetween one end of said yoke and said shaft.
 8. The invention as definedin claim 1, wherein: said driver means includes a magnetic circuithaving a fixed magnetic yoke including an elongated, non-circularmagnetic shaft spaced a short distance therefrom, a maximum flux beingestablished in said magnetic circuit when said shaft is located in oneangular position, a minimum flux being established in said magneticcircuit when said shaft is located in another angular position, means torotate said shaft, means to establish A magnetomotive force in saidmagnetic circuit, said conductive loop being located between one end ofsaid yoke and said shaft.
 9. An electromagnetic actuator comprising: abase; a movable conductive loop for connection to a member to bemechanically actuated by movement thereof; means to guide movement ofsaid conductive loop on said base in the plane of said conductive loop;connecting means selectively operable to open and to short circuit saidconductive loop; and driver means to produce magnetic flux in a locationlinking said conductive loop, said driver means causing the amount ofsaid linking flux to change abruptly for inducing a current in saidconductive loop.
 10. The invention as defined in claim 9, wherein: saidconnecting means includes a selectively operable switch which can beopened or closed, said switch being connected in series with saidconductive loop to short circuit the same when the switch is closed,said abrupt change in flux leaving said conductive loop motionless whensaid switch is open, said abrupt change in flux causing a force to beapplied to said conductive loop when said switch is closed, said forcebeing transmitted to said member to move the same, closure of saidswitch permitting a current to be induced in said conductive loop whichinduced current produces its own magnetic field that reacts with thatproduced by said driver means and causes said force to be applied tosaid conductive loop.